Tractor overturns are a major cause of agricultural-worker deaths each year. These deaths and serious injuries may have been prevented if the tractors had been equipped with a rollover protective structure (ROPS), and the operator was wearing a seat belt. NIOSH estimates that of the 4.61 million tractors utilized in the United States, 61 percent were manufactured before 1971. For many of these older tractors, ROPS are not available. If ROPS can be mounted to the axles of older tractors, then the control of this potential hazard can be attained. The objective of this project is to use ROPS testing simulations and laboratory and field testing of ROPS to develop suitable guidelines so that ROPS can be designed to be mounted on older tractors. The specific objectives are to: 1) Examine existing tractor surveys to identify the make and model number of older tractors currently in use in the United States. 2) Categorize the older tractors in terms of similar axle designs and define the major categories of older tractor axle designs. 3) Utilize Finite Element modelling to analyze each major category of axle design to determine the relative axle strengths and identify which major axle categories will support ROPS loadings. 4) Investigate axle and mounting modifications for each major axle category to allow ROPS to be mounted on older tractors. 5) Utilize laboratory and field testing to investigate ROPS design for the major axle categories of pre-ROPS tractors. Tests will be conducted in accordance with ASAE 5519. 6) Investigate vibrational loading of ROPS to examine fatigue failures on pre-ROPS tractor axles. 7) Develop guidelines for the design and mounting of ROPS on older tractors. The design guidelines will concentrate on axle housing support and mounting modifications and locations.